Question 1

Which of the following best explains why phospholipids spontaneously form bilayers in aqueous environments?

Accepted Answer

Their amphipathic nature causes hydrophilic heads to interact with water and hydrophobic tails to avoid water.

Question 2

A researcher is studying a cell membrane that is unusually rigid at room temperature. Which of the following changes to the membrane composition would most likely increase its fluidity?

Accepted Answer

Increase the proportion of unsaturated fatty acids in the phospholipids.

Question 3

Which of the following statements about cholesterol in biological membranes is correct?

Accepted Answer

Cholesterol helps maintain membrane integrity by preventing extremes in fluidity at both high and low temperatures.

Question 4

A cell is exposed to a sudden drop in environmental temperature. Which membrane adaptation would help the cell maintain membrane fluidity?

Accepted Answer

Increase the proportion of unsaturated fatty acids in the membrane.

Question 5

Which of the following best describes the 'fluid mosaic model' of biological membranes?

Accepted Answer

A phospholipid bilayer with proteins embedded within and on the surface, allowing lateral movement of components.

Question 6

Which of the following changes would most likely decrease the permeability of a cell membrane to small, nonpolar molecules?

Accepted Answer

Increase the proportion of saturated fatty acids in the membrane.

Question 7

A scientist compares the membrane composition of salmon living in arctic waters to those in tropical waters. What difference would they most likely observe?

Accepted Answer

Arctic salmon have a higher concentration of unsaturated fats and higher cholesterol levels compared to tropical salmon.

Question 8

Which of the following is a function of glycolipids and glycoproteins in the plasma membrane?

Accepted Answer

Cell-cell recognition and labeling for packaging and distribution.

Question 9

Which of the following best explains why soaps and detergents can dissolve oils and dirt in water?

Accepted Answer

They are amphipathic molecules that form micelles around hydrophobic substances, allowing them to dissolve in water.

Question 10

Which of the following would most likely occur if a membrane's fatty acid tails were lengthened?

Accepted Answer

The membrane would become less fluid and less permeable.

Question 11

A mutation causes a cell to produce only saturated fatty acids in its membrane phospholipids. Which of the following is a likely consequence?

Accepted Answer

The membrane will be less fluid and more rigid, especially at lower temperatures.

Question 12

Which of the following is a key difference between integral and peripheral membrane proteins?

Accepted Answer

Integral proteins span the membrane and have hydrophobic regions, while peripheral proteins are attached to the membrane surface.

Question 13

Which of the following best describes the effect of increasing temperature on membrane fluidity?

Accepted Answer

Increasing temperature increases membrane fluidity.

Question 14

A cell membrane is composed of phospholipids with mostly unsaturated fatty acids. Which of the following is most likely true about this membrane?

Accepted Answer

It will be more fluid and more permeable than a membrane with mostly saturated fatty acids.

Question 15

Which of the following is a direct consequence of the amphipathic nature of phospholipids?

Accepted Answer

Formation of bilayers with hydrophobic tails facing inward and hydrophilic heads facing outward.

Question 16

Which of the following best explains why cholesterol is considered a 'buffer' for membrane fluidity?

Accepted Answer

It prevents the membrane from becoming too fluid at high temperatures and too rigid at low temperatures.

Question 17

A cell is exposed to a toxin that prevents the lateral movement of phospholipids. Which of the following processes would be most directly affected?

Accepted Answer

The ability of membrane proteins to diffuse and interact within the membrane.

Structure and Function of Biological Membranes

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